Adaptive windowing in mechanically-steered intravascular ultrasound imaging: Ex vivo and in vivo studies with contrast enhancement

Intravascular ultrasound (IVUS) is utilized frequently in vascular diseases such as coronary artery disease and peripheral vascular disease. Many techniques-including but not limited to IVUS-seek to characterize plaques in coronary artery disease in order to determine which are likely to rupture. Biologists have recently identified the development of intra-plaque vasa vasorum, small vessels which supply the coronaries with oxygen and nutrients, as a potential indicator of plaque vulnerability. By imaging plaques with penetrating vasa vasorum, high resolution contrast-enhanced ultrasound imaging may allow identification of vulnerable plaques prior to rupture. Here we present processing techniques for improving spatial resolution and image contrast in mechanically steered ultrasound imaging based on minimum variance (MV) beamforming and the phase coherence factor (PCF). In tissue-mimicking phantom studies, PCF processing improved CTR by a mean of 4.2 dB, while combined MV and PCF processing improved spatial resolution by 41.7%. These processing strategies may improve image quality in both conventional B-mode IVUS and contrast-enhanced IVUS.